CVE-2025-39825 (GCVE-0-2025-39825)
Vulnerability from cvelistv5 – Published: 2025-09-16 13:00 – Updated: 2026-08-05 12:05
VLAI
EPSS
VEX
Title
smb: client: fix race with concurrent opens in rename(2)
Summary
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix race with concurrent opens in rename(2)
Besides sending the rename request to the server, the rename process
also involves closing any deferred close, waiting for outstanding I/O
to complete as well as marking all existing open handles as deleted to
prevent them from deferring closes, which increases the race window
for potential concurrent opens on the target file.
Fix this by unhashing the dentry in advance to prevent any concurrent
opens on the target.
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-10 20:41 UTC
Assigner
References
7 references
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
78c09634f7dc061a3bd09704cdbebb3762a45cdf , < c9e7de284da0be5b44dbe79d71573f9f7f9b144c
(git)
Affected: 78c09634f7dc061a3bd09704cdbebb3762a45cdf , < 24b9ed739c8c5b464d983e12cf308982f3ae93c2 (git) Affected: 78c09634f7dc061a3bd09704cdbebb3762a45cdf , < c9991af5e09924f6f3b3e6996a5e09f9504b4358 (git) Affected: 78c09634f7dc061a3bd09704cdbebb3762a45cdf , < 289f945acb20b9b54fe4d13895e44aa58965ddb2 (git) Affected: 78c09634f7dc061a3bd09704cdbebb3762a45cdf , < d84291fc7453df7881a970716f8256273aca5747 (git) |
guessed | |
| Linux | Linux |
Affected:
5.13
Unaffected: 0 , < 5.13 (semver) Unaffected: 6.1.150 , ≤ 6.1.* (semver) Unaffected: 6.6.104 , ≤ 6.6.* (semver) Unaffected: 6.12.45 , ≤ 6.12.* (semver) Unaffected: 6.16.5 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix) |
guessed | |
| Siemens | SIMATIC CN 4100 |
Affected:
0 , < V5.0
(custom)
|
guessed |
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}
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"status": "final",
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"vulnrichment": {
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"timestamp": "2026-06-10T20:41:27.081852Z",
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"value": "AV:L - The race is driven entirely by local syscalls \u2014 one thread in `rename(2)`/`renameat2(2)` reaching `cifs_rename2()` and another in `open(2)` hitting the still-hashed target dentry via `lookup_fast()`. No network peer initiates the attack; a remote SMB server can only widen the window by delaying responses.\nAC:L - The attacker owns both sides of the race and the window is enormous \u2014 it spans an unbounded `netfs_wait_for_outstanding_io()` wait, deferred-close teardown, and a full SMB round trip plus a 3-iteration retry loop. The attacker can widen it arbitrarily by keeping I/O outstanding on the target, making it trivially winnable with a simple rename/open loop.\nPR:L - Any unprivileged local user with ordinary access to a directory on an already-mounted CIFS/SMB share can call rename(2) and open(2); no capabilities are required. Mounted SMB shares are routine on enterprise desktops, autofs home directories, and containers with CIFS volumes.\nUI:N - Both racing threads are the attacker\u0027s own; no victim action is needed. The presence of an SMB mount is a standing system configuration, not a per-exploit user interaction.\nS:U - The corruption of dcache/deferred-handle state and the resulting file damage stay entirely within the kernel and the mounted filesystem\u0027s own security authority. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - A handle opened inside the race escapes `cifs_mark_open_handles_for_deleted_file()` and remains on `tcon-\u003eopenFileList`, where `cifs_get_readable_path()` matches cached handles by path string \u2014 so a later `open(2)`/`read(2)` of that path can be served from the stale handle to the pre-rename file, disclosing unbounded contents of a file (potentially another user\u0027s) that should no longer be reachable at that name.\nI:H - The racing open makes the target appear busy, driving `cifs_rename2()` into the `unlink_target:` path that deletes the target file and retries \u2014 on retry failure the file\u0027s data is destroyed while rename(2) reports an error (the documented data-loss mode fixed by the later `c5ea3065586d`). The same stale path-matched handle also lets writes land on the wrong server-side object.\nA:H - By keeping opens and I/O active on the still-hashed target, the attacker prevents `netfs_wait_for_outstanding_io()`\u0027s `io_count` from ever reaching zero, pinning the renaming task in unkillable uninterruptible sleep while it holds the parent directory\u0027s `i_rwsem` exclusively \u2014 starving all other operations in that directory and triggering hung-task warnings (panic with `hung_task_panic=1`)."
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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